The use of infusion and feeding sets to administer solutions and food to a patient is well known in medical arts. Infusion and enteral sets are used for both enteral and parenteral application, respectively. For hygienic reasons the infusion and enteral sets must be disposed of immediately after use, making it single-use equipment which may be recycled afterwards. Enteral feeding pumps are used to provide the patient with nutrition and medication (formula) when they are unable, for a variety of reason, to eat normally. Parenteral (intravenous) solutions are provided to patients to ensure adequate hydration and to provide needed nutrients, minerals or medication. Often, the enteral or infusion set is placed in a free standing arrangement in which gravity forces the formula or solution into the patient. The rate at which the solution enters the patient can be roughly controlled by various clamps, such as roller clamps, which are currently available on the market.
In many applications, it is necessary to precisely control the amount of solution or formula which enters the patient. When this is the case, a regulating device such as an infusion pump, is placed along the infusion set to control the rate at which the solution is fed to the patient. In applications where a pump etc. is used the clamps or valves used to regulate flow are typically open to their fullest extent to prevent the clamp or valve from interfering with the proper functioning of the pump. The clamp or valve is opened with the expectation that the enteral feeding pump or infusion will control fluid flow through the enteral or infusion set. However, emergencies or other distractions may prevent the medical personnel from properly loading the enteral or infusion sets in the enteral feeding pump or the infusion pump. Furthermore, the enteral or infusion sets may be inadvertently dislodged from the pump during operation of the pump.
In many enteral feeding systems the engagement of the pump tube to the rotor controls the flow of fluid to the patient according to the speed of the rotor (peristaltic pump). In the event the enteral feeding set is not properly mounted to the pump, an excess flow of fluid through the feeding set can occur under force of gravity known as free-flow often develops which is highly undesirable. Under a free-flow condition, an amount of solution or formula many times the desired dose can be supplied to the patient within a relatively short time period. This can be particularly dangerous if the solution contains potent medicine or the patient's body is not physically strong enough to adjust to the large inflow of solution or formula.
U.S. Pat. No. 6,224,578 discloses a valve device which is incorporated into the lower portion of a drip chamber for preventing the free flow of fluid through a tube assembly when the tube assembly is disengaged from a pump of a fluid administration system, while permitting fluid flow when the tube assembly is engaged around a rotor of the pump. The valve device comprises a valve body having a top component sealingly engaged with a bottom component. The top component is integrally formed with the lower portion of the drip chamber and defines a plurality of axial fluid passageways formed around a stationary plunger which seals against a opening formed at the upper portion of the bottom component. The opening is in communication with a lumen that extends into a hollow tube assembly which is attached to the bottom component of the valve body. The bottom component further includes a flex joint made of a flexible material that is adapted to flex and pull the opening away from the plunger to establish fluid flow through the valve device. In operation, a user applies a tensile force along the tube assembly by engaging the tube assembly around a rotor of a pump which pulls the flex joint away from the plunger and opens the valve device to fluid flow therethrough by gravity. When the tube assembly is disengaged from the rotor the flex joint is forced back to its original position such that the plunger is sealed against the opening, thereby preventing fluid free-flow through the fluid administration system. The '578 patent comprises the features of the preamble of claim 1 of the present invention.
United States Published Patent Application 2003/0229309 describes an anti-free-flow device for a fluid administration system having a tube assembly engageable with a pump with one end of the tube assembly connected to a source of fluid and the other end in fluid flow communication with a patient. The valve device comprises a tube portion defining a channel in-line along a portion of the tube assembly and a body disposed and securely retained inside the channel. Fluid flow is allowed through the tube assembly whenever the tube assembly is in a stretched condition, such as when the tube assembly is engaged with the pump. However, fluid free-flow is prevented whenever the tube assembly is in a relaxed condition or disengaged from the pump.
The anti-free-flow devices of the known kind as describe above suffer from a number of disadvantages such as the fact that they tend to block the rather viscous enteral nutrition fluids which may contain a high percentage of fibres. This is due to the fact that the lumina of the valves are too small so that fibres may get stuck in the small openings and lumina. Thus, in many cases the use of anti free-flow valves in enteral feeding systems has been avoided whereby the necessary safety measures have been neglected.
Further, the handling of the silicone tubing in a peristaltic pump is related with high stretching or tensional forces of an AFF valve. Most of the prior art valves reduce the lumen for the fluid flow thus increasing the tendency to block viscous enteral nutrition fluids. Thus, there is a need for an anti free-flow device that overcomes some of the above-mentioned disadvantages of the prior art.
It is therefore the object of the present invention to provide a valve for engaging with a tube to be used in an enteral feeding or infusion pump which withholds overstretching forces of the tubing, is simple in structure and small in size, reliable in function, easy to handle and compatible with the majority of existing pump devices, in particular peristaltic pumps. This object is achieved by the combination of features of the claimed invention. Particularly advantageous embodiments of the invention are subjects of the dependent claims.